Telephone system



May 20, 1941, B. c. BELLOWS EIAL TELEPHONE SYSTEM 2 Sheets-Sheet 1 Filed Nov. 2, 1939 uvvmroks a BELL W5 By L.L.EAGON ATTORNEY to serve all lines of the ofiice.

Patented May 20, 1941 STTES TENT OFFIQ TELEPHONE {SYSTEM Application November 2, 1939, Serial No. 302,540

6 Claims. (Cl. 179- 27) This invention relates to telephone systems and more particularly to circuits and apparatus applicable thereto for controlling the registration at a central oflice of the identification of either a calling or called subscribers line.

in the establishment of connections to toll of the exchange area, it is essential that theticketing mechanism be supplied with the identification of the calling subscribers line. It is therefore the object of the present invention to provide means of a simple and reliably operating character which will transmit line identifying information to an operators position or to a regis-.

tering device.

One embodiment of the invention for controlling the transmission and registration of calling line identifying information comprises a plurality of impedance modifiers, one for each line of an exchange area, each modifier comprising an impedance coil and a constantly rotating rotor disc associated with the poles of the magnetic circuit of said coil. The disc is provided with asmany groups of notches in its edge as there are identifying digits in the calling line designation, each group of notches correspondingto one of the digits of the number. For convenience the discs of modifiers allocated to each subgroup of lines are mounted on a common shaft driven at a constant speed by a motor, as many of such assemblies of modifiers being supplied as are necessary The impedance coils of the modifiers are normally open-circuited but the coil of the modifier of any line is connected to the sleeve terminal of such line following the initiation of a call from the line by the operation of the line cut-ofi relay.

The sleeve terminal of the calling line is extended, following the establishment of a connection from the calling line, to a calling line identifying equipment at which equipment a source of high frequency tone current is applied to the incoming end of the extended sleeve circuit. At the equipment, a vacuum tube detector is inductively coupled to the sleeve circuit for controlling a digit registering device.

When a calling subscriber has initiated a call, and the subscribers line has been extended to the equipment, tone current is applied over the sleeve circuit of the established connection through the impedance coil of the modifier allocated to such calling line, the rotor of which in completing a revolution modulates the tone current in accordance with the groups of notches in the edge of the rotor. These modulations are then detected by the tube at the equipment which tube controls relays to transmit register controlling impulses to a registering mechanism.

In accordance with a further embodiment, the invention is also applicable to the transmission of impulses under the control of a subscribers dial for setting a selector switch or for setting a register mechanism to register dialed digits.

For a better understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawings in which:

Fig. 1 schematically discloses one embodiment of the invention;

Fig. 2 shows the rotor of one of the impedance modifiers disclosed in the lower left portion of Fig.

Fig. 3 shows a further modification of a rotor;

Fig. 4 shows an alternative form of an impedance modifier;

Fig. 5 shows the invention as applied to a dialing system;

Fig. 6 shows a further modification of the impulse receiving apparatus in which the impulses are amplified to operate an alternating current impulse responsive relay; and

Fig. 7 shows a further modification of the impulse receiving apparatus in which the impulses are received directly by an alternating current impulse responsive relay.

Referring first to Fig. 1, a plurality of subscribers lines A, B and C of a subgroup of lines is disclosed, each having an impedance modifier allocated thereto and each terminating in the bank of a line finder LF. The line finder is associated with the first group selector S which in turn has access to a trunk circuit T assumed to terminate in a toll operators position. The line finder LF and selector switch S may be of any well-known type. At the operators position, a calling line identifying equipment CLI, disclosed in the right portion of the figure is provided for controlling the registration of the digits of the calling line identification number transmitted thereto over the connection established over the selector switches by the impedance modifier allocated to the calling line.

Each impedance modified, for example, the

modifier Ma allocated to the calling line A comprises a disc I of magnetic material mounted on a shaft 2 which is driven at a constant speed through gears 3 and 4 by a motor 5. As illustrated, the discs of the modifiers allocated to a subgroup of lines, for example, all of the lines accessible to a group of line finders, are mounted on a common shaft, as many of such assemblies being provided as there are line-finder groups. Associated with each disc is an impedance or field coil 6 having a core I, the pole-pieces 8 of which are positioned adjacent to the faces of the disc I near the periphery thereof.

As disclosed more clearly in Fig. 2, each disc I is provided with groups of notches inits periphery which are filled with any suitable dielectric material. The disc I shown in Fig. 2 appertaining to the impedance modifier Ma, allocated to the calling line A whose directory number is assumed to be 2228, is thus provided with four oupsof notches 9, H), II and I2 comprising respectively 2, 2, 2, and 8 notches. The disc is also provided with a longer preliminary starting notch I3 for a purpose to belater described. From this construction it will be noted that when a metallic portion of the disc I is interposed between the pole-pieces 8 of the impedance coil 6, the magnetic reluctance of the magnetic circuit of the coil 6 is relatively low, but that when a dielectric portion of the disc is interposed, the reluctance will be raised, thus as the disc rotates between the pole-pieces, the impedance of the coil 6 will be modified in accordance with the dielectric insentions in the periphery of the disc and consequently in accordance with the directory number of the subscribers line to which the disc is allocated.

When a subscriber, for example, the subscriber on line A initiates a call, the line finder LP is started and seizes the calling line whereupon the cut-off relay Id of the line is operated. These operations are performed in the well-known manner. It will be assumed that the calling subscriber desires a toll connection and therefore dials the digit zero to obtain a connection with the toll o-perators position and that .in response to dialing the selector switch S is positioned to seize an idle trunk T terminating at a toll operators position. Upon the seizure of the trunk the cut-off relay M is operated over the extended sleeve connection by current supplied from the source 22 through retard coil 2i and a circuit is established from ground through the winding of coil 6 of the impedance modifier Ma, over the contacts of relay I l, sleeve terminal I 5 of the calling line, sleeve brush I6 of the line finder LF, sleeve brush ll of selector switch S, sleeve terminal S8 of the trunk T, primary winding of input transformer I9 and the secondary winding of tone coil 20 to ground. High frequency tone current from the tone current source 23 is thereupon applied through the windings of the tone coil 20 through the winding of impedance coil 8 of impedance modifier Ma.

The secondary winding of input transformer I 9is connected to the input circuit of detector tube 24, the output circuit of which is connected to the winding of the anode or pulsing relay 25. During the negative half cycles of the tone source 23, the potential impressed therefrom upon the input circuit of tube 2 3, through the windings of input transformer I 9 will be negative and the tube 24 which has its grid 25 negatively biased will not become conducting; During the positive half cycles of the tone source 23, the potential impressed upon the input circuit of tube 24 will be positive tending to overcome the negative bias on the grid 26. During such positive half-wave cycles, if the impedance of the coil 6 is high as when metallic portions of the disc I are interposed between the pole-pieces 8, the positive potential impulses applied from the source 23 are of such a value that the tube 24 will not become conducting, but if the impedance of the coil 6 is low as when dielectric portions of the disc I are interposed between the pole-pieces 8, the positive half-wave impulses from the source 23 will render the grid 26 of tube 24 sufficiently positive to cause the tube to become conducting.

It will now be assumed that at the time the previously traced circuit for coil 6 was established, the disc I was in such a rotational position that the group of notches I2 with their dielectric inserts are passed between the pole-pieces 8 during the continued rotation of the disc and that as 'a consequence eight modulating impulses are transmitted to the input circuit of tube 24 causing the tube to become conducting in response to each impulse to operate relay 25. Upon each operation, relay 25 establishes a circuit from ground over its front contact, over the back contact of relay 2'! through the winding of slow-tooperate relay 23 and battery to ground. Since each operation of relay 25 is of short duration, the closures of the circuit of relay 28 are of too short duration to cause the operation of relay 28 and the transmission of such impulses is without effect on the registration equipment of the calling line identification circuit.

As soon, however, as the disc I rotates to position the longer starting notch I3 between the pole-pieces 8, a modulating impulse of a longer duration is transmitted and relay 25 responding thereto is maintained operated for a sufficient interval to permit slow-to-operate relay 28 to operate and look over its left contacts to ground supplied by the digit registering equipment 29. When this long impulse terminates, relay 25 releases and with relay 28 operated, establishes a circuit from ground over its back contact, the right contacts of relay'28 through the winding of relay *2! to battery and ground whereupon relay ZIoperates, looks over its left contacts to ground supplied by the digit registering equipment 29, opens at its right back contacts the initial operating circuit of relay 28 and at its right front contacts prepares an impulsing circuit over which impulses may thereafter be transmitted to the digit'registering equipment by the following energizations and releases of relay 25.

As disc I continues to rotate, two modulating impulses are transmitted as the two notches of the group 9 pass between the pole-pieces'8 and relay'25 is operated and released twice to transmit two register controlling impulses to the thousandsregister of the digit'registering equipment. When the transmission of the two impulses is terminated'and relay 25 remains deenergized for the interval measured by the time required for the disc I to position the succeeding group of notches ID between the pole-pieces 8, the usual transfer operation is performed in the digit registering equipment preparatory to registering the next or hundreds digit. In a similar manner as the notches of groups I 0, II and I2 of disc I pass between pole-pieces 8, series of modulating im- .2, the tens digit '2 and the units digit 8, by the hundreds, tens and units registers or the digit registering equipment. As soon as all of the digits of the calling line identification number have been registered, relay 30 in the digit registering equipment is operated in any desired manner to open the locking circuits of relays 2'! and 28 which relays thereupon release.

By the provision of the starting notch l3 in the disc I and the relays 21 and 28, the circuit insures that no digit impulses can be registered until the disc reaches its starting position and therefore the impulses transmitted to designate the thousands, hundreds, tens and units digits will be correctly registered in the proper order by the registers of the digit registering equipment 29.

The digit registers may cause the lighting of lamps to display the line number registered to enable the toll operator to check the number given to her by the calling subscriber or may cause the printing of the number on a toll ticket if the identification circuit is used in connection with automatic ticketing mechanism.

As disclosed in Fig. 3, the dielectric material may be omitted from the notches in the edge of disc I. As illustrated in this figure, groups of notches 3i, 32, 33 and 34 are formed to transmit series of modulating impulses to identify a line whose number is 9000. If desired the pole-pieces of the impedance coil may be associated with the disc I as shown in Fig. 4, one pole-piece 8' of the impedance coil 6' being associated in close relationship to one face of the disc I near its center and the other pole-piece 8' being closely associated with the same face of the disc near its periphery.

Fig. shows the invention as applied to a telephone system in which an impedance modulator controlled by a subscribers dial is employed to transmit impulses to a central office for controlling the setting of a selector switch directly in response to such impulses or for controlling the setting of a registering mechanism which may be used for any desired purpose. In accordance with Fig. 5, the usual substation dial mechanism is replaced with an impedance modulator which comprises a disc M of magnetic material mounted on a shaft 42 to which is secured a ratchet wheel 43. Cooperating with the ratchet wheel is a pawl 44 pivoted on the spring returned dial 45. The disc 4! is provided with ten equally spaced notches in its periphery. Associated with the disc is an impedance coil 46 having a core 41, the pole-pieces 48 of which are positioned adjacent to the faces of the disc near the periphery thereof. It is to be understood that the dial controlled modulator would be equipped with contact springs, not shown, rtor shunting out the substation apparatus during the operation thereof.

At the central oiiice an impulse responsive equipment is provided comprising the detector tube 54 and the impulse responsive relay 55 which equipment becomes associated with the calling line through the windings of input transformer 49 when the calling subscriber initiates a call and causes the line finder LF to connect with the terminals of the calling line. The primary winding of transformer 49 is connected serially in the calling line loop, through the secondary winding of tone coil 50 and the negatively poled battery 5|,

and the secondary winding is connected to the input circuit of detector tube 54. The primary winding of tone coil 50 is connected to a source 53 of high frequency tone current.

When the subscriber moves the dial 45 ofi normal to the finger stop to dial a digit, the pawl 44 connected to the dial moves freely over as many teeth of ratchet wheel 43 as correspond to the finger hole in which the subscriber has inserted his finger and when thereafter the dial is released and returns to normal under control of its return spring, the pawl causes the rotation of the ratchet wheel and the associated disc 4|.

The disc 4| will thus cause a number of its pe-' ripheral notches corresponding to the value of the digit dialed to pass between the pole-pieces 48 thus transmitting modulated impulses over the loop circuit including the winding of impedance coil 46 and the primary winding of transformer 49 which impulses are effective to cause the tube 54 to become conducting in response to each impulse and to operate and release the impulse responsive relay 55 in the manner previously described. Relay 55 may control any desired digit registration apparatus as previously stated.

If desired the detector tube 54 may be replaced by an amplifier tube 56 as disclosed in Fig. 6 havin an alternating current impulse responsive relay 51 associated with its output circuit or the tube may be omitted as disclosed in Fig. 7 in which case the alternating current relay 5'! would be directly responsive to the impulses transmitted by the modulator. It will be obvious that the modified impulse receiving circuits dis-closed in Figs. 6 and '7 could equally well be applied to the circuit disclosed in Fig. l.

To prevent inductive interference between the sleeve circuits of trunks which may be included in the same cable, the tone sources of the several impulse receiving equipments may be of diiierent frequencies and the detector tube circuits may be tuned to be responsive only to the frequency of their respective tone sources.

What is claimed is:

1. In a signaling system, a line circuit, an impulse responsive device comprising a detector tube having its input circuit associated with one end of said line circuit and having an impulse responsive relay in its output circuit, means for applying a high frequency current to said line circuit and an impulse transmitting means associated with the other end of said line circuit comprising a yoke of magnetic material, a field coil on said yoke connected in series with said line circuit and. a notched disc of magnetic material rotatable between the poles of said yoke whereby the rotation of said disc transmits modulating impulses over said line circuit to cause the operation of said responsive relayin synchronism with said impulses.

2. In a signalling system, a line circuit, an impulse responsive device comprising a detector tube having its input circuit associated with one end of said line circuit and having an impulse responsive relay in its output circuit, means for applying a high frequency current to said line circuit and an impulse transmitting means associated with the other end of said line circuit comprising a yoke of magnetic material, a field coil on said yoke connected in series with said line circuit and a notched disc of magnetic material rotatable between the poles of said yoke, a dial movable from its normal position in accordance with different digital values, means for returning said dial to normal, and means operable in the return movement of said dial for rotating said disc to generate a number of modulating impulsesin said line circuit proportional to the movement of said dial to cause the operation of said relay in response thereto.

3. In a calling line number identifying system,

a calling line, means for extending a connection from said line to a central office, an impulse responsive means and a registering equipment responsive thereto at said central office, said impulse responsive means comprising a detector tube the input circuit of which is associable with a conductor of said established connection and the output circuit of which is provided with an impulse responsive relay for controlling said registering equipment, means for applying a high frequency current to said conductor, and means individual to said calling line for transmitting modulating impulses over said conductor in accordance with the designation of said calling line comprising a yoke of magnetic material, a field coil thereon associable with said conductor and a disc of magnetic material rotatable between the poles of said yoke and having groups of notches in its periphery corresponding to the digits of the calling line number.

4. In a calling line number identifying system, a plurality of calling lines, means for extending a connection from any one of said lines to a central otflice, an impulse responsive means and a registering equipment responsive thereto at said central ofiice, said impulse responsive means comprising a detector tube, the input circuit of which is associable with a conductor of said established connection and the output circuit of which is provided with an impulse responsive relay for controlling said registering equipment, means for applying a high frequency current to said conductor, and means individual to each of said lines for transmitting modulating impulses over said conductor in accordance with the designation of the calling line associated with the outgoing end of said conductor, comprising a yoke of magnetic material having a field coil thereon associable with the outgoing end of said conductor and a disc of magnetic material rotatable between the poles of said yoke and having groups of notches in its periphery corresponding to the digits of the number of the calling line to which it is individual and a common driving shaft upon which the discs of a plurality of said transmitting means are mounted for simultaneous rotation.

5. In a calling line number identifying system, a calling line, means for extending a connection from said line to a central office, an impulse responsive means and a registering equipment responsive thereto at said central ofiice, said impulse responsive means comprising a detector tube the input circuit of which is associable with a conductor of said established connection and the output circuit of which is provided with an impulse responsive relay, a slow-operating pick-up relay operable only upon a long operation of said impulse responsive relay, a register conditioning relay operable upon the operation of said pick-up relay and the subsequent release of said impulse responsive relay whereby the subsequent operations and releases of said impulse responsive relay are effective to operate said registering equipment, means for applying a high frequency current to said conductor, and means individual to each calling line for transmitting modulating impulses over said conductor in accordance with the designation of said calling line, comprising a yoke of magnetic material, a field coil thereon associable with the outgoing end of said conductor and a disc of magnetic material rotatable between the poles of said yoke and having in its periphery a relatively wide pick-up notch and groups of narrower notches corresponding to the digits of the calling line number.

6. In a calling line number identification system, a calling line, means for extending a connection from said line to a central office, an impulse responsive means and a registering equipment responsive thereto at said central ofiice, said impulse responsive means comprising a detector tube the input circuit of which is associable with the sleeve conductor of said established connection and the output circuit of which is provided with an impulse responsive relay for controlling said registering equipment, means at said central oilice for applying a high frequency current to said sleeve conductor, means individual to said calling line for tran mitting modulating impulses over said conductor in accordance with the designation of said calling line comprising a yoke of magnetic material, a field coil thereon and a disc of magnetic-material rotatable between the poles of said yoke and having groups of notches in its periphery corresponding to the digits of the calling line number, and means responsive to the extension of said calling line for connecting said field coil to the outgoing end of said conductor.

BRIAN C BELLOVJS. LLOYD L. EAGON. 

